Packaging machines, so-called tray closing machines, are known in which products are packaged into pre-fabricated tray-shaped containers and closed with a film.
From DE 690 03 503 a packaging machine is known in which the packaging containers are transported from a filling station onto a plate in a sealing station by means of circulating drivers. It is disadvantageous that the positioning of the containers takes place in an imprecise way and takes a lot of time since the acceleration must remain low and the drivers must return from the region of the sealing station.
From EP 680 880 a machine is known in which the containers are directly transported from a supply unit into a closing device (sealing station) by pusher arms and, at the same time, the closed containers are removed from the closing device. Here as well, the containers are positioned on plates in the sealing station. However, the positioning is imprecise and the transport takes a lot of time since a supply and a removal can only take place when the sealing station is opened and during this time no operation for evacuating, introduction of gas and sealing of the containers is possible.
In these packaging machines the sealing station is arranged in the main transport path of the containers between a supply device and a removal device and a specific amount of containers is each time inserted into the sealing station, thereafter sealed therein and after sealing transported on to the removal device. Not until this is finished, the following containers can be transported into the sealing station and, therefore, the process in the sealing station takes a relatively long time since not only the time of sealing but additionally the transport time arises. During this time the containers to be sealed next have to wait until the sealing station becomes vacant.
Furthermore, the applicant knows an improved packaging machine in which two receiving plates for receiving the containers are provided in the sealing station. In a position which is located in the main transport path of the containers from the supply conveyor belt to the removal device, sealed containers are removed from one receiving plate and the receiving plate is supplied with containers to be sealed while, on the other receiving plate in a second position which is located lateral of the main transport path, containers are sealed with the upper film in a sealing tool. This leads to an increase of the effective operating time of the sealing tool and, thus, the operating speed of the packaging machine can be increased.
In the known packaging machine the two receiving plates are located on a rotary table and the motion of the receiving plates into the respective other position is performed by a rotation of the rotary table around a vertical axis. A relatively large space is needed in the horizontal direction perpendicular to the main transport path for the rotary motion which is in particular problematic when the packaging machine is used in small rooms. Furthermore, relatively long trajectories have to be covered between the two positions of the receiving plates in the rotary motion and accelerations having rotary components as well as translatory components occur, thus limiting the possible transport speed.